1. Technical Field
The present invention pertains to a cooling device and a cooling method and particularly relates to a cooling device and a cooling method that cool a portable electronic device.
2. Related Art
In recent years, radiation detectors such as flat panel detectors (FPD) where an X-ray sensitive layer is disposed on a thin-film transistor (TFT) active matrix substrate and which can directly convert X rays into digital data have been put to practical use. Further, portable radiological image conversion devices (also called “electronic cassettes” below) that use these radiation detectors to generate image data representing a radiological image expressed by irradiated radiation and to store the generated image data have been put to practical use.
Since these electronic cassettes are portable, patients lying on a stretcher or a bed can be shot as they are. Further, since the place that is to be shot can be adjusted by changing the position of the electronic cassette, these electronic cassettes can flexibly accommodate patients who cannot move.
These electronic cassettes detect weak signals generated by irradiated radiation and generate image data representing a radiological image. However, it is known the problem that the detection result of the signals is sometimes inconsistent due to the affect of heat generated by electronic circuits inside the electronic cassettes and image quality is dropped.
As technologies for solving this problem, in Japanese Patent Application Laid-Open Publication (JP-A) No. 2000-116633 and JP-A No. 2003-194951, there are described technologies that control the transmission of heat generated by the electronic circuit to the radiation detector by disposing a shield member between the electronic circuit and the radiation detector or by disposing a heat dissipating component that transmits heat generated by the electronic circuit to a casing of the electronic cassette in an electrically insulated state.
Further, in JP-A No. 10-177224, there is described a technology where a ventilation opening and a fan are disposed in a casing of an X-ray shooting device and air is allowed to pass through the ventilation opening to cool the entire device.
Further, in JP-A No. 2002-311526, there is described a technology where a lid that is capable of opening and closing a casing of an electronic cassette is disposed, a heat absorbing member is detachably provided at the inside of the casing, and heat is absorbed by the heat absorbing member.
Moreover, in JP-A No. 2006-102492, there is described a technology where a storage container is manufactured in a dimension such that an electronic cassette is capable of being housed therein and the temperature of the storage container is adjusted to a desired temperature.
However, although the technologies described in JP-A No. 2000-116633 and JP-A No. 2003-194951 can control a drop in image quality resulting from the affect of heat emission from the electronic circuit when only a short amount of time is needed to drive the electronic cassette, heat also reaches the radiation detector as the temperature of the entire electronic cassette rises when a long amount of time is needed to drive the electronic cassette. Therefore, these technologies cannot control a drop in image quality resulting from the affect of heat emission.
Further, sometimes electronic cassettes are used in operation sites, and it is demanded that electronic cassettes have a sealed structure because sterilization is performed in order to prevent blood-borne infections and the like. However, the technology described in JP-A No. 10-177224 cannot be given a sealed structure because its structure allows air to circulate through the ventilation opening, so this technology cannot be applied as an electronic cassette cooling mechanism.
Further, the technology described in JP-A No. 2002-311526 is complicated because it is necessary to manually replace the heat absorbing member inside the casing. Therefore, as the casing of the electronic cassette is opened and closed, deterioration of the sealed structure of the electronic cassette becomes a problem.
Moreover, the technology described in JP-A No. 2006-102492 is convenient but its structure is complex and expensive. Further, although it is good that numerous electronic cassettes can be used alternately in order as in the embodiment in JP-A No. 2006-102492, when one or two electronic cassettes are repeatedly used, the electronic cassettes cannot be sufficiently cooled, and sometimes a drop in image quality resulting from the affect of heat emission cannot be controlled.